External Non-Specific Defences

Question 1

What are 6 examples of external non-specific defences?

Answer 1

Skin, mucous membranes, hairs, acids, lysozymes, flushing.

Question 2

How does the skin work as an external defence?

Answer 2

Forms a physical barrier against the entry of pathogens.
Secretes sebum, which kills some bacteria.
Secretes sweat, the salts and fatty acids of which prevent the growth of some bacteria.

Question 3

How do mucous membranes work as an external defence?

Answer 3

Line areas that the skin doesn’t cover and secrete mucous, which inhibits the entry of microorganisms.
e.g. respiratory tract, reproductive tract, digestive tract, urinary tract

Question 4

How do hairs work as an external defence?

Answer 4

Trap particles, and prevent them from entering the body.

Cilia move mucous filled with microorganisms out of the body.

Question 5

How do acids work as an external defence?

Answer 5

Kills or reduces the amount of microorganisms. Stomach juices, vagina and sweat all contain acid.

Question 6

How do lysozymes work as non-specific defences?

Answer 6

Enzyme which kills bacteria.

Found in sweat, tears, saliva, tissue fluid, and cerumen.

Question 7

How does cerumen provide an external non-specific defence?

Answer 7

(AKA earwax)
Acidic, which inhibits or kills bacteria.
Contains lysozymes, which kill bacteria.

Question 8

Explain how flushing acts as an external non-specific defence.

Answer 8

Moves fluids out of the body, removing pathogens.

Question 9

Identify four protective reflexes against pathogens.

do not mention in test unless specifically asked

Answer 9

Sneezing

Coughing

Vomiting

Diarrhoea